docs: def encode_value(value):
      # type: (bytes) -> bytes
      """Encodes the value in Length-Value format.
  
      :param value: Value to encode
      :type value: six.string_types or :class:`boto3.dynamodb_encryption_sdk.types.Binary`
      :returns: Length-Value encoded value
      :rtype: bytes
      """
      return struct.pack(">I{attr_len:d}s".format(attr_len=len(value)), len(value), value)